Isomerization of paraffins



Patented Dec. 14, 1943 2,336,863 ISOMERIZATION F PARAFFINS Aristid V. Grosse, Bronxville, N. Y., and Herman Pines, Riverside, Ill assignors Products Company, of Delaware to Universal Oil Chicago, 111., a corporation No Drawing. Application January 29, 1943, Serial No. 474,012

8 Claims. (Cl. 260-6835) This application is a continuation-in-part of our co-pending application, Serial No. 282,083, filed June 30, 1939, which in turn is a continuation-in-part of our application, Serial No. 118,587, filed December 31, 1936.

This invention relates particularly to the isomerization of normally liquid straight chain paraffin hydrocarbons to produce more highly branched compounds.

boiling point and specific gravity both decrease while the antiknock value as expressed by octane number generally increases although figures are not available for the neopentane. Similarly, the isomeric hexanes, heptanes, and octanes will show the same progressive relationships as their structure becomes more condensed. As the molecular weight of paramn hydrocarbons increase, 'the number of possible and known isomers increases In a more specific sense the invention is ap- 10 more than arithmetically so that in cases of isoplicable not only to individual parafiin hydromerization involving mixtures of n-parafilns and carbons of straight chain structure but also to p rt ularly n-parafiins in admixture with other hydrocarbon mixtures containing these comhydrocarbons in gasolines, the determination of pounds in substantial percentages such as the extent of isomerization is not possible by straight run gasolines and their fractions, which analytical methods but can be estimated from contain in addition to paraiiin hydrocarbons of the observed change in antiknock value. highly knocking characteristics other hydrocar- In one specific embodiment, the present inbons comprising some parafiins of branched vention comprises treatment of parafiin hydrochain structure and the usual run of naphthenes carbons or hydrocarbon mixtures containing suband aromatics. stantial percentages thereof, such as straight The isomerization of individual normally liquid run gasoline fractions with catalysts comprising paraffin hydrocarbons such as normal pentane, metal halides of the Friedel-Crafts type and and normal hexane is frequently desirable in the hydrogen halides to eflect isomerization reacmanufacture of derivatives since the isomeric tions. There are several alternative catalysts compounds are more reactive and, in the case of which may be employed in accomplishing the gasoline or gasoline fractions containing various isomerization reaction among paraflin hydrocarnaphthenic hydrocarbons, the isomerization has bons and although they may be used more or less the eiiect of increasing the antiknock value of the interchangeably, some are more efiective than gasolines to a marked extent as will be shown in others and it is not intended to infer that they later examples. are definitely equivalent.

There should be no need for extensively re- Among the compounds which may be used are counting the number of possible isomers of such metallic halides of the Friedel-Crafts' type parafiln hydrocarbons since these are all preas the halides of aluminum, zinc, iron and zirdictable on the present theories of organic chemconium either alone or in admixture with one istry and are well known to those familiar with another. Extensive experiments have indicated this subject. However, the following table is that it is essential that a hydrogen halide be shown to indicate in a general way the change added in the reaction zone along with these comin structure and properties of normal parafiin pounds to obtain satisfactory results. These hydrocarbons and their isomers, particularly catalysts may be used alone or impregnated upon since the pentanes constitute some of the lower- 40 various types of adsorbent carriers to produce boiling constituents of ordinary gasolines. granular catalysts utilizable either in liquid,

Compound Formula gg? Density f gr c. n-Peutane cmwnmcm 36.3 0.6475@0O.--.- 63

i-Pcntanc--.-. oncmcm 2s o.esa4 oo.-- as Neo-pentane..... C(CH|)| 9.5 0.625l@14.4 O..-

It will be observed from the above that as the structure of the molecule becomes more compact,

mixed or vapor phase operation. At temperatures above those boiling points where distillation of the catalyst is to be avoided, superatmospheric pressures may be employed. There are also some variations in the relative amounts of metal halides and hydrogen halides used at optimum treating conditions but the determination of these ratios is somewhat a matter of experiment.

We have determined that by the use of the class of catalysts mentioned, and particularly by the concurrent use of considerable simeratmospheric, pressures, normally liquid paraflln hydrocarbons of straight chain structure, and particularly the normal compounds may be converted into hydrocarbons of more highly branched structure with yields of the order or 50-60%. Such yields are obtainable at temperatures within the approximate range of 50-250 C. and superatmospheric pressures. Evidently the use of superatmospheric pressures of the order of 1 to 200 atmospheres and preferably 10 to 200 atmospheres at temperatures of 150 C. and higher, besides depressing the volatilization of metal halide catalysts tends also to depress numerous undesirable side reactions which would result in the formation of hydrogen and low molecular weight hydrocarbons, so that the reaction proceeds more or less in one direction until an equilibrium is established.

While inert gases such as nitrogen may be employed in producing the necessary pressure. experiments have shown that it is preferable to employ hydrogen which seems to minimize undesirable side reactions involving decomposition rather than the desired isomerization. As is customary in hydrogenation processes, the hydrogenation reactions are fostered by increase in pressure and in some instances, pressures of 2000 pounds per square inch or higher produce beneficial effects when the hydrocarbon involved tends to undergo decomposition under the isomerizing conditions.

The process may be operated under batch or continuous conditions either in liquid, mixed. or

vapor phase as may be desirable or expedient in view of the particular catalyst combination shown and the particular hydrocarbon mixture undergoing treatment. A simple method of operation consists in adding 5 to of granular anhyd mis aluminum chloride to a treating vessel containing hydrocarbons and rov ded with a me-- sure'if nece sary. The solid cata yst is then kept in sus ension by mo erate ag tation bv introducinc a slow stream of hydrogen chloride.

Vapor phase operations ma be conducted by passing vapors of hydrocarbons mixed with a small amount of hydroaen chloride over solid granular catalysis compris ng the preferred metal halides. an example of such catalyst being g anular al m num c lor de o a comp site produced by im regnating solid adsorbents with alum num chloride. In the use of'a readily vaporizable catalvst such as aluminum chloride. it may be ublimed directly into a stream of hydrocarbon vapors and hydrogen chloride followed by settling of the spent catalyst and fractionation of the products.

The following examples are introduced to indicate in a general way the nature of the results obtainable in the operation of the process, but they are not given with the intention of limiting the scope of the invention in exact correspondence with the numerical data at present.

assasea Example I The vapors of normal pentane mixed with about 1 percent by volume of hydrogen chloride were passed through a mass of granular catalyst comprising 10 to 20 mesh particles of activated carbon base supporting about an equal weight of anhydrous aluminum chloride. The temperature employed was 200 C. and a pressure of 450 pounds per square inch was maintained to depress the volatilization of the aluminum chloride. The vapors of 25 parts by weight o1 n-pentane were passed over 30 parts by weight of the composite catalyst per hour. Fractionation of the products indicated that the once-through yield of isopentane was about 27% by volume of the n-pen tane charged. There was produced in addition 3.5% by volume of isobutane and 3.5% by volume of n-butane. By operating continuously and recycling the unconverted normal compound the flnal overall yield of isopentane was approximately Example II In this example a gasoline fraction boiling within the range of 50-90 C. and obtained from a highly parafiinic Michigan gasoline was treated. The fraction had an octane number of 54 and corresponded roughly to a mixture of heXanes, since n-hexane boils at about 70 C. This fraction was subjected to isomerlzation for the improvement of its antlknock value in the presence 0! aluminum chloride and hydrogen chloride at two temperatures to observe the eii'ect at each. The gasoline fraction was placed in a pressure vessel, aluminum chloride was added and the heating was conducted over a period of six hours. after which the vessel was cooled and the gaseous and liquid products recovered and examined. The following table gives the principal results obtained in the two runs:

Run #1 Run #2 Temperature 0.- 200 Charge in treater "gasoline," parts by weig 200. 0 200. 0 MP1. do 20.0 20.0 BC] do 6 5 Maximum pressure ..atmospheres.. i6 45 PRODUCTS OF THE REACTION PER CENT BY I Approximate.

The foregoing runs show a considerable increase in antiknock value with only moderate losses. By a limited chemical treatment further quantities of the hydrocarbons recovered by the hydrolysis of the lower aluminum chloride sludge layer are rendered utilizable in the gas oline layer so that the overall yield is still higher than that shown. The butane can be further utilized by successive steps of dehydrogenation and polymerization to still further augment the yield of motor fuel fraction.

Example 111 The vapors of normal pentane mixed with about 1 per cent by volume of hydrogen chloride were passed through a mass of granular catalyst comprising 10 to 20 mesh particles of activated carbon base supporting about an equal weight of anhydrous aluminum chloride. The temperature employed was 200 C. and a pressure of 450 pounds per square inch was maintained to depress the volatilization of the aluminum chloride. The vapors of 25 parts by weight of normal pentane were passed over 30 parts by weight of the composite catalyst per hour. Fractionating of the products indicated that the once-through yield of isopentane was about 27% by volume of the normal pentane charged. There was produced in addition 3.5% by volume of isobutane and 3.5% by volume 01 normal butane. By operating continuously and recycling the unconverted normal compound the final overall yield of isopentane was approximately 80%.

Example IV 71 parts by weight of diatomaceous earth was mixed with 29 parts by weight of anhydrous aluminum chloride, and placed in a pressure vessel. 4% by weight of hydrogen chloride gas was introduced and the contents of the yessel were placed under a pressure of 25 atmospheres by the introduction of dry hydrogen. After heating the vessel for a period of three hours at a temperature of approximately 250 C. during agitation, it was found that the aluminum chloride was exactly adsorbed on the diatomaceous earth so that an apparently dry material was formed.

Normal pentane vapors containing about 2% by weight of hydrogen chloride was passed through the catalyst at a temperature of 190 C. and a pressure of 400 pounds per square inch. There was produced about 25% by volume of isopentane based on the volume of normal pentane charged as a once-through yield. Some side reactions occurred as indicated by the presence of about 5% by volume of lower and 5% by volume of higher boiling hydrocarbons. In recycle operation, the ultimate yield 01 iso-pentane was approximately 70%.

Example V 70 parts by weight of pumice was mixed with 32' parts of substantially anhydrous aluminum chloride and heated in a pressure vessel at 250 C. under 25 atmospheres of hydrogen pressure in the presence of 4-5% by weight of hydrogen chloride gas as in the two preceding examples.

The vapors of normal pentane containing approximately 2% by weight of hydrogen chloride were passed over the above catalyst at a temperature of 180 C. under a pressure of 400 pounds per square inch. In a once-through run, the yield of iso-pentane was approximately 20% and this was increased to an ultimate yield of 65% by recycling operations.

Ewample VI The vapors of normal pentane containing approximately 4 mol per cent of hydrogen chloride were passed over a solid granular catalyst comprising zinc chloride on an adsorbent alumina (25% by weight of zinc chloride) at a temperature of 274 C. under a pressure of 1500 pounds per square inch. The charge rate was equivalent to a liquid hourly space velocity measured as volumes of charge per volume of catalyst space per. hour of 0.27. The once through yield of isopentane was 21.4% and upon recycling was increased to an ultimate yield of approximately 63%.

Example VII An acid washed commercial pentane-hexane fraction having an octane number of 57.7 was passed over the same type catalyst as used in An isomerized product having an octane number of 70 is produced.

Example VIII Normal pentane containing approximately 4 mol per cent of hydrogen chloride was contacted with a catalyst comprising iron chloride on alumine by weight iron chloride) at a temperature of 275 C. under a pressure of 1500 pounds. Liquid hourly charge rate measured as liquid volumes of charge per volume of catalyst space per hour was about 0.25. In a once.

through run the yield of isopentane was approximately 20% and this was increased to an ultimate yield of 62% by recycling.

The nature of the present invention and its practical aspects can be seen from the foregoing specification and examples although neither section is intended to impose undu limitations upon the proper scope of the invention. 7

We claim as our invention:

1. A process for increasing the antiknock properties of a normally liquid hydrocarbon fraction boiling in the gasoline range and containing parafiins of relatively low antiknock value which comprises subjecting the hydrocarbon fraction under isomerizing conditions of temperature, pressure and time to the action 01 an'isomerizing catalyst of the Friedel-Crafts type in the presence of an added hydrogen halide and correlating the amount of hydrogen halide and said isomerizing conditions of temperature, pressure and time to convert a substantial portion of the parafiins contained in said fraction into isomers thereof having the same molecular weight as and of higher antiknock properties than said parafllns.

2. A process for increasing the antiknock properties of a normally liquid hydrocarbon fraction boiling in the gasoline range and containing normal paraflins of less than 7 carbon atoms to the molecule which comprise subjecting the hydrocarbon fraction under isomerizing conditions of temperature, pressure and time to the action of an isomerizing catalyst of the Friedel-Crafts type in the presence of an added hydrogen halide and correlating the amount of hydrogen halide and said isomerizing conditions of temperature, pressure and time to convert a, substantial portion of the parafiins contained in said fraction into branched chain parafiins of the same molecular weight.

3. A process for isomerizing a normally liquid paraflln hydrocarbon boiling in the gasoline range which comprises subjecting said paraflin under isomerizing conditions of temperature,

pressure and time to the action of an isomerizing catalyst of the Friedel-Craits type in the presence of added hydrogen halide and correlating the amount of hydrogen halide and said isomerizing conditions of temperature, pressure and time to convert a substantial portion of said paraffin into an isomer or isomers thereof having the same molecular weight as saidparaflin.

4. A process for isomerizing a normally liquid parafiin hydrocarbon boiling in the gasoline range which comprises subjecting said paraflin under isomerizing conditipns of temperature, pressure and time to the action of an aluminum halide in the presence of added hydrogen halide and correlating the amount or hydrogen halide and said isomerizing conditions of temperature, pressure and time to convert a substantial portion of said' paraiiin into an isomer or isomers thereof having the same molecular weight as said parafiin.

5. A'process for isomerizing a normally liquid paraflin hydrocarbon boiling in the gasoline range which comprises subjecting said paramn under isomerizing conditions of temperature, pressure and time to the action of an isomerizing catalyst of the Friedel-Craits type in the presence of added hydrogen halide. said temperature being in the approximate range of 50 C. to 250 0., and correlating the amount of hydrogen halide and said isomerizing conditions of temperature, pressure and time to eflect, as the principal reaction in the process, the conversion of a substantial portion of said parafiln into an isomer or isomers thereoi having the sam molecular weight as said paraflin.

assesses 6. A process for isomerizins a normally liquid paraflin hydrocarbon boiling in the gasoline range which comprises subjecting said paraflin under isomerizing conditions of temperature, pressure and time to the action of an isomerizing catalyst of the Friedel-Craits type in the presence of added hydrosen halide, said temperature being in the approximate reuse of 50 C. to 250 C. and said catalyst being supported on a solid carrier material. and correlating the amount at hydrogen halide and said isomerizing conditions of temperature. pressure and time to convert a substantial portion of said paraiiln into an isomer or isomers thereof having the same molecular weight as said parailin.

.7. The process as defined in claim 5 further characterised in that said catalyst-comprises an aluminum halide.

8. The process as defined in claim 6 furthe characterised in that said catalyst comprises an aluminum halide.

ARISTID V. GROSSE. HERMAN PINES. 

